Energy storing foot prosthesis with improved plantar flexion

ABSTRACT

A prosthetic foot characterized by an easily exchangeable auxiliary ankle member demountably attached to forefoot and sole portions, which are in turn demountably and interchangeably connected. The forefoot, heel and auxiliary ankle portions are fabricated from polymer impregnated and encapsulated laminates, including such laminates as carbon fibers and/or fiberglass or synthetic fibers such as Kevlar. The easily demountable connection of the auxiliary ankle permits interchangeability thereof to match the activity schedule of the wearer utilizing the prosthetic foot without the necessity of frequent visits to the prosthetist. A compressible member between the forefoot member and the sole member, and function blocks located between the various members provide additional adjustability. The orientation of the auxiliary ankle member and compressible member also allows for increased plantar flexion.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. ProvisionalApplication No. 60/229,113, filed Aug. 30, 2000, the entirety of whichis hereby incorporated by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to foot prostheses in general, andspecifically to a prosthetic foot characterized by a unitary foot andheel construction, and an auxiliary ankle construction which permits theflexibility of the prosthesis to be selectively determined and easilychanged.

[0004] 2. Background of the Invention

[0005] Although many prosthetic devices have attempted to simulate theambulation of a normal foot, very few of them are readily adjustable interms of their performance characteristics. Adjustability is especiallydesirable among amputees who frequently participate in a variety ofphysical activities requiring varying levels of energy-storing and-releasing attributes.

[0006] Certainly, some prior art devices more nearly achieve the desiredease of adjustability than do others. For example, see my U.S. Pat. No.4,547,913 for my invention relating to a “Composite Prosthetic Foot andLeg,” U.S. Pat. No. 4,822,363 for my invention relating to a “ModularComposite Prosthetic Foot and Leg,” my U.S. Pat. No. 5,181,932 for myinvention relating to a “Foot Prosthesis Having Auxiliary AnkleConstruction” and U.S. Pat. No. 5,290,319 for my invention relating to a“Prosthetic Foot Incorporating Adjustable Bladders” Also my U.S. Pat.Nos. 5,037,444 and 6,071,313 discloses a prosthetic foot device withsimilar preferred materials and methods of manufacture, and withcorresponding benefits therefrom. Each of these patents is incorporatedby reference herein.

[0007] Notwithstanding the valuable contribution and characteristics ofmy aforementioned patented foot prostheses and specifically themodularity thereof, the adjustment of those prostheses is relativelyinvolved. Any adjustment of the performance characteristics of thoseprostheses basically requires the disassembly of a covering shroud (ifpresent) and of structural members from each other and specifically fromthe pylon tube (through bolt, nut, and washer combinations, forexample). After a new combination of structural members has beenselected, it typically must similarly be reassembled. Disassembly of theprosthetic foot from the pylon requires a significant amount of time,effort, and money as it must be done by a prosthetist.

[0008] Other prosthetic foot devices are even less readily adjusted, andinclude U.S. Pat. No. 3,335,428 to Gajdos, which attempts to duplicatethe skeletal and skin structure of a natural human foot, U.S. Pat. No.2,075,583 to Lange, which incorporates a rubber form mounted inoperative relationship with a rigid metallic core, and U.S. Pat. No.4,645,509 to Poggi, which teaches a prosthetic foot incorporating amonolithic keel or beam of relatively massive proportions intended toreact to the load of an amputee's body during walking, running, jumping,and the like and to release the resultant stored energy to create footlift and thrust complementing the amputee's natural stride.

[0009] Moreover, the dynamic performance of many of these other priorart devices is relatively stiff and immediate, and generally cannotproduce adequate plantar flexion during heel strike, while retainingsufficient stiffness for toe-off.

SUMMARY OF THE INVENTION

[0010] It is, therefore, one object of my invention to provide a footprosthesis which can be easily adjusted without the necessity ofremoving the foot from the vertical pylon of an amputee's prostheticleg. This will allow an active amputee to participate in a wide varietyof activities without the necessity of frequent visits to theprosthetist.

[0011] In one embodiment, the present invention provides a footprosthesis characterized by an easily removable auxiliary supportmember, herein also termed an auxiliary ankle, in conjunction with aprimary support member, herein termed the forefoot member, and a lowersupport member, herein termed the sole member. The primary and lowersupport members are of such character as to be easily adaptable toprovide size adjustment or accommodation of different spring rates tosuit the size of foot, or of the stride and weight of the amputee. Theauxiliary support member provides further adjustment to accommodatevarying activity levels of a given amputee. The ease of removal of theauxiliary support member provides a degree of quick and easy adjustmentpreviously unobtainable with prior prosthetics.

[0012] These members are preferably fabricated, for example, frompolymer impregnated and encapsulated laminates, including such laminatesas carbon fibers and/or fiberglass or synthetic fibers such as Kevlar.Such members provide desirable energy-storing and -releasingcharacteristics.

[0013] Another object of the invention is the incorporation in aprosthetic foot of the aforementioned character of compressible membersin order to achieve a gradual dynamic transition, which can furtherimprove the degree of adjustability of the prosthesis.

[0014] The particular location of attachment of the auxiliary supportmember allows for increased performance. Plantar flexion can beincreased by not limiting the flexibility of the forefoot portion duringheel strike, yet the ankle portion is still stiffened by the auxiliarysupport member during toe off. The inclusion of compressible membersdisposed between the auxiliary support member, and the forefoot memberallows for further adjustability of performance characteristics.

[0015] Other objects and advantages of the invention will be apparentfrom the following specification and the accompanying drawings, whichare for the purpose of illustration only.

[0016] For purposes of summarizing the invention and the advantagesachieved over the prior art, certain objects and advantages of theinvention have been described herein above. Of course, it is to beunderstood that not necessarily all such objects or advantages may beachieved in accordance with any particular embodiment of the invention.Thus, for example, those skilled in the art will recognize that theinvention may be embodied or carried out in a manner that achieves oroptimizes one advantage or group of advantages as taught herein withoutnecessarily achieving other objects or advantages as may be taught orsuggested herein.

[0017] All of these embodiments are intended to be within the scope ofthe invention herein disclosed. These and other embodiments of thepresent invention will become readily apparent to those skilled in theart from the following detailed description of the preferred embodimentshaving reference to the attached figures, the invention not beinglimited to any particular preferred embodiment(s) disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Having thus summarized the general nature of the invention andits essential features and advantages, certain preferred embodiments andmodifications thereof will become apparent to those skilled in the artfrom the detailed description herein having reference to the figuresthat follow, of which:

[0019]FIG. 1 is a side elevation view of one preferred embodiment of aprosthetic foot;

[0020]FIG. 2 is a side elevation view of an alternative embodiment of aprosthetic foot;

[0021]FIG. 3 is a top view of the foot of FIG. 1;

[0022]FIG. 4 is a front elevation view of the foot of FIG. 1;

[0023]FIG. 5 is a top view of an alternative embodiment of a prostheticfoot;

[0024]FIG. 6 is a front elevation view of the foot of FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Referring to the drawings, and particularly to FIG. 1, I show onepreferred embodiment of a foot prosthesis 10 constructed in accordancewith the teachings of the invention. The foot 10 generally includes aforefoot member 80, a sole member 50, and an auxiliary support member 86operatively and demountably attached to each other at the arch section44. Attachment is preferably accomplished using suitable nut and boltcombinations 104 associated with a load-transmitting metallic plate 106.The auxiliary member is preferably attached to the forefoot member suchthat the auxiliary member may add to the stiffness of the ankle portionof the forefoot member. If desired, a retaining band 70 may be providedat the ankle section 80. A compressible member 116 may be providedbetween the auxiliary member, and the forefoot member. Function blocks118, 120, 121, and 119, FIG. 2 may also be provided in order to vary thelength of the effective lever arms of the various members. If indicated,the forefoot and sole portions can be permanently secured to each other,as by epoxy adhesive, a polyurethane resilient layer, or the like.

[0026] The forefoot member 80 preferably includes a substantially rigidupper attachment section 40, a forward and downward curving anklesection 42, an arch section, 44, and a distal toe section 46. Thesections 40, 42, 44, and 46 are preferably formed integrally with oneanother and simultaneously by the incorporation of a plurality oflaminae embedded in a hardened, flexible polymer.

[0027] In the particular embodiment shown, the sole member 50 includesan attachment section 58 and a heel section 54 extending substantiallyrearward from said attachment section 58. The sections 58 and 54 arepreferably formed integrally with one another and simultaneously by theincorporation of a plurality of laminae embedded in a hardened, flexiblepolymer as described herein.

[0028] The auxiliary support member 86 includes a lower section 94 andan upper section 88. Said lower section 94 of the auxiliary supportmember 86 is rigidly attached to said forefoot member 80 and said solemember 50 with nut and bolt combinations 104, and extends substantiallyrearward and upward, its uppermost edge 88 preferably terminating belowsaid attachment section 40 of said forefoot member 80.

[0029] In an alternative embodiment, shown in FIG. 2, the sole member 50extends substantially forward from said attachment section to theforwardmost tip 48 of the foot 10, and the forefoot member 80 preferablyextends slightly forward from the forwardmost tip 84 of the auxiliarysupport member 86, curving slightly upwards to a distal tip 45. In thisalternative embodiment, a block 119 can be interposed between the tip 45of the forefoot portion 80, and the toe section 52 of the sole member50.

[0030] Resilient blocks of wedge-shaped configuration and of varioussize may be included, for example in the positions indicated in thedrawings as 118, 120, 121, and 119, FIG. 2, such that they allow for thevariability of the lever arms of the structural members 80, 86, and 50.For example FIG. 1 shows a block 118 interposed between the undersurface of the forward portion 84 of the auxiliary ankle 86 and theupper surface of the arch section 44 of the forefoot member 80, whichhas the effect of decreasing the lever arm of the toe portion 46 of theforefoot member 80.

[0031] Referring to FIGS. 3 and 4, the attachment section 40 of theforefoot member 80 preferably incorporates two centrally-locatedopenings 90. The attachment section 40 is substantially rigid andcapable of sustaining torsional, impact and other loads impressedthereupon by the toe portion 46 and heel portion 54 of the prosthesis.In addition, the inherent rigidity of the attachment section 40 causesthe effective transmission of the aforesaid loads imposed thereupon to asuitable ancillary prosthetic pylon 30, by bolt and nut combinations 98assembled through openings 90 to a pylon coupling 33. A screw 92 orother suitable attachment means secures the ancillary pylon 30 in thecoupling 33. Those skilled in the art will recognize that a variety ofother attachment means may be utilized, such as glue, rivets, tape, etc.

[0032] In an alternative embodiment shown in FIGS. 5-8, the sole member50 and part of the forefoot portion 80 are bifurcated into multipleside-by-side foot portions such that they are capable of movementindependent from one another. Preferably, the foot is bifurcated by theprovision of a slot in said forefoot and sole portions. A strap 74 orsimilar expedient may be provided to limit the movement of theside-by-side foot portions relative to each other, if desired. Theauxiliary ankle member described herein would also be preferablyincluded in this embodiment. The concept of the split foot is describedin detail in my U.S. Pat. No. 6,071,313 which is incorporated herein byreference.

[0033] A compressible member 116 may be disposed between said forefootmember 80 and said auxiliary support member 86. The compressible member116 is preferably fabricated such that it provides additional adjustmentof the performance characteristics of the prosthesis 10 through thevariation of its degree of compressibility. For example, an inflatablebladder filled with air, CO₂ or other gas could be used. In aparticularly preferred embodiment of the present invention thecompressible member 116 may comprise a compressible foam member. A foammember provides a low-cost compressible member for energy storage andrelease, and avoids the inherent potential difficulties of air bladderssuch as leakage and risk of puncture. The foam member also provides aslight dampening of the prosthetic foot which improves the overallresponse characteristics and provides a more natural feeling foot.

[0034] The compressible member 116 may be molded or fabricated from awide variety of resilient materials, as desired, such as natural orsynthetic rubber, plastics, polyurethane, honeycomb structures or anyone of a variety of other materials well known to those skilled in theart for storing and releasing energy. Cellular foam is preferred toprovide a desirable spring characteristic and a more natural stride. Forexample, expanded polyurethane such as cellular Vulkolka PUR-CELL No.15-50 with a density of approximately 500 kilograms per cubic meter,available from Pleiger Plastics Company of Washington, Pa., may be usedto form the compressible member 116. Foam densities of between about 150and 1500 kg/m³ may also be used to obtain the benefits of the inventiontaught herein.

[0035] The rear surface of the auxiliary ankle member 86 is preferablyallowed to slip relative to the compressible member 116 in order toallow for increased plantar flexion. The compressible member 116 may beheld in place by glue, velcro, snaps, or a variety of other methods asrecognized by one skilled in the art such that the preferred slippingbetween the auxiliary ankle member 86 and the compressible member 116 isallowed.

[0036] Alternatively, the compressible member 116 may be replaced by asubstantially non-compressible friction-reducing element, or eliminatedaltogether. The absence of the compressible member 116 would cause thewearer to experience more resistance to motion during toe-off, while itspresence allows for slower, more gradual resistance during toe-off.Either or both of these cases may be desirable depending on the activityfor which the foot is needed.

[0037] Toe pads 130 and/or a heel pad 126 may be disposed under the toesection 46 of the forefoot member 80 and the heel section 54 of the solemember 50 respectively, so as to provide minor shock absorption to theprosthetic 10.

[0038] In the preferred embodiment, bolt and nut combinations 104, inconjunction with the load-distributing metallic plates 106, serve tosecure the sole member 50 in operative relationship with the forefootmember 80 of the prosthesis. This mode of affixation facilitates theassembly or dismounting of selected sole members 50 in operativerelationship with selected forefoot members 80, thus permitting a widerange of different sizes and stress load response characteristics to berelated to each other to accomplish the optimum functionalcorrespondence between the primary and sole portions 80 and 50.

[0039] The auxiliary ankle member 86 provides further adjustability ofthe performance characteristics of the prosthetic 10 by adding to thestiffness of the forefoot member 80. The auxiliary ankle 86 is formedfrom fibrous laminates of the same character as the various portions ofthe prosthesis 10. In a preferred embodiment of the present invention,the auxiliary ankle 86 incorporates an attachment section 94 which isoperatively associated with the ankle section 42 of the forefoot member80 and the attachment section 58 of the sole member 50.

[0040] The auxiliary ankle 86 is preferably secured in operativerelationship with the curvilinear ankle section 42 of the forefootmember 80 through the aforementioned assembly of the bolt and nutcombinations 104. On its end opposite from the attachment section 94,ankle member 86 has an upper section 92 which is preferably fixed inoperative relationship with a compressible member 116 and thecurvilinear ankle section 42 of the forefoot member 80 by the use of aflexible, yet substantially non-stretching strap 70. Said compressiblemember 116 providing a gradual dynamic transition throughout toe-off.

[0041] The strap 70 may be fabricated from a suitably tough, flexiblematerial such as impregnated canvas or the like, and is configured andassembled with the ankle section 42 of the forefoot member 80, theauxiliary support member 86, and/or the compressible member 116 toachieve desired stress-storage and -release performance in theprosthesis. For example, the strap 70 may be releasably attached aroundthe auxiliary support member 86 through the provision of Velcro-typefasteners or similar expedient.

[0042] A restraining element such as the strap 70 may be incorporated atvarious locations on the prosthesis 10 to restrict the distance thatassociated structural members 86, 80, and 50 may move from one anotherin order to control the performance characteristics of said foot. Forexample, one skilled in the art will recognize that increased distanceof motion between the auxiliary support member 86 and forefoot member 80during heel strike will allow for increased plantar flexion. Theretaining element may be utilized to prevent undesirable excessiveloading and stressing of a particular member 86, 80, or 50, and/or tocombine the spring-stress response characteristics of the associatedstructural members 12 under certain loading conditions. For example, thestrap 70 as assembled in FIG. 1 permits the auxiliary member 86 toassist in raising the toe 46 of the prosthesis 10 and to store andrelease spring energy when the heel portion 54 is struck on the groundin front of the wearer. The retaining element may be eithersubstantially elastic, or substantially static depending on the degreeof relative motion desired.

[0043] In the preferred embodiment, the auxiliary ankle member 86 issecured against the relatively concave surface of the curvilinear anklesection 42, so that the anticipated upward deflection of a toe section46 of the forefoot member 80, as more thoroughly described below, willeventually cause deformation of the auxiliary ankle 86 as well asdeformation of the ankle section 42, effectively combining thedeformation resistance and energy storage characteristics of theauxiliary ankle member 86 with those of the forefoot member 80.Alternative embodiments would include securing the auxiliary ankle 86 tothe underside of the arch section 44 and continuing to use the strap 70to maintain the functional relationship between the auxiliary ankle 86and the forefoot member 80 in order to achieve the aforedescribeddesired combination of the deformation resistance and energy storagecharacteristics of the auxiliary ankle member 86 with those of the anklesection 42.

[0044] The auxiliary ankle member 86 can be provided with differentnumbers of laminates to make it more or less compliant to loadstransmitted through the forefoot member 80. Consequently, whenconfronted with various anomalies in an amputee, such as overweight orexcess activity levels, the basic structure of the forefoot member 80,and more particularly the ankle section 42, can be materially modifiedto provide ankle portion action which is precisely adjusted to the needsof the amputee. Moreover, a variety of auxiliary ankle members 86 can bemade available to an active amputee, allowing the flexibility of theprosthesis to be adjusted on the basis of the particular activity whichthe amputee is undertaking. Furthermore, the location of the point ofattachment at the arch section 44 allows exchange of auxiliary anklesections 86 to be made without necessarily removing the prosthesis 10from the pylon 30.

[0045] A cosmetic cover (not shown) can be provided to shroud theprosthesis 10 after the optimum assemblage of the primary and solemembers 80 and 50 and an auxiliary ankle member 86 has beenaccomplished. The cosmetic cover, which may be formed of low-densityformed polymer, is not required to serve any ancillary shock-absorbingor other stress-isolating function since all of the loads imposed uponthe prosthesis can be absorbed, transmitted and reasserted in a mannerto be described in greater detail below.

[0046] The materials from which the forefoot member 80, sole member 50,and the auxiliary ankle 86 are formed preferably possess the ability toprovide an energy-storing, resilient, spring-like effect. This ispreferred because each engagement of the prosthesis 10 with an adjacentsurface impresses compression, torsional and other loads upon theprosthesis 10 which are stored within the prosthesis and then, dependentupon the stride of the wearer, re-impressed upon said surface to achievea natural stride conforming, ideally, in all respects to the stride ofthe unimpaired limb of the wearer of the prosthesis 10.

[0047] These members are preferably fabricated, for example, frompolymer impregnated and encapsulated laminates. To achieve therelatively thin construction of the forefoot and sole members 80 and 50and the auxiliary support member 86 of the prosthesis 10, the aforesaidpolymers are utilized in conjunction with various laminating materials.Various types of fibrous laminae can be utilized to achieve thecontinuum required by the design of the forefoot and sole members 80 and50 and the auxiliary support member 86 to complement thestress-absorbing and storing characteristics of the polymers in whichsaid fibrous laminae are embedded.

[0048] Of course, there is a wide variety of fibrous reinforcements inthe form of laminae available at the present time, including suchinorganic fibers as glass or carbon fibers. These inorganic fibers arecustomarily provided in tape or sheet form and can be readilysuperimposed in the mold to permit them to be encapsulated in theselected polymer.

[0049] Obviously, the number of superimposed laminae and the lengthsthereof, together with the thickness of the encapsulating polymer,determine the stress characteristics of the resultant forefoot and solemembers 80 and 50 and the auxiliary support member 86 and,correspondingly, determine the total weight of the prosthesis 10. Aswill be apparent from the discussion herein, the forefoot and solemembers 80 and 50 and the auxiliary support member 86 are designed tospecifically accommodate individuals having different foot sizes,different weights and different strides and the individual design of theforefoot and sole members 80 and 50 and the auxiliary support member 86provides for matching, to an extent previously unknown in the art, thenatural characteristics of the wearer's uninjured limb.

[0050] Furthermore, the function blocks 118, 120, 121 and 119, FIG. 2can be provided in different sizes and in materials having differentcompression characteristics so that the respective lever arms and thecorresponding deflections of the heel section 54 and the toe section 46or 52 may be increased or decreased.

[0051] It will be understood by those of skill in the art that the termssuch as ankle, heel portion, arch and forefoot portion are used hereinas convenient references to describe the general function and/orlocation of the various portions of the prosthesis and are not intendedto indicate that the prosthesis has a structural configurationreplicating these anatomical structures of the human foot.

[0052] Although this invention has been disclosed in the context ofcertain preferred embodiments and examples, it will be understood bythose skilled in the art that the present invention extends beyond thespecifically disclosed embodiments to other alternative embodimentsand/or uses of the invention and obvious modifications and equivalentsthereof. Thus, it is intended that the scope of the present inventionherein disclosed should not be limited by the particular disclosedembodiments described above, but should be determined only by a fairreading of the claims that follow.

What is claimed is:
 1. A prosthetic foot comprising: a primary supportmember capable of supporting the amputee, and of providing energystorage and release, said primary support member having a substantiallyvertical attachment section, an intermediate curvilinear ankle sectioncurving downward and forward from said upper section, an arch sectionextending forward and downward from said ankle section, and a toesection extending substantially forward from said arch section, said toesection providing a lever arm for said foot, said upper section beingnon-rotatably securable to a pylon member, socket or other prostheticleg member intermediate said foot and the stump of an amputee; anauxiliary support member having an upper section and a lower section,said auxiliary support member being secured at said lower sectionthereof to said arch section of said primary support member, saidauxiliary support member extending substantially rearward and upwardgenerally along said primary support member, said upper sectionterminating substantially near said attachment section of said primarysupport member; whereby said auxiliary support member can be removed andexchanged without removing said foot prosthesis from said prosthetic legmember.
 2. The prosthetic foot of claim 1 additionally comprising alower support member having an attachment section and a heel section,said attachment section of said lower support member being secured withone or both of said auxiliary support member or said primary supportmember at a point along said arch section of said primary supportmember, said lower support member extending substantially rearward suchthat bending stress is distributed substantially evenly throughout saidlower support member during heel strike, said heel section providing alever arm for said foot.
 3. The prosthetic foot of claim 1 wherein arestraining element is used to limit the movement of one member of saidprosthesis relative to another member.
 4. The prosthetic foot of claim 3wherein said restraining element is a strap of substantially flexibleand non-stretchable material.
 5. The prosthetic foot of claim 3 whereinsaid restraining element is a strap of substantially flexible andstretchable material.
 6. The prosthetic foot of claim 1 additionallycomprising a substantially non-compressible element of friction-reducingmaterial disposed between said lower section of said auxiliary supportmember, and said toe section of said primary support member.
 7. Theprosthetic foot of claim 1 additionally comprising a resilientcompressible member disposed between said upper section of saidauxiliary ankle member and said ankle section of said primary supportmember, said compressible member being fabricated from a compressiblefoam.
 8. The prosthetic foot of claim 5 wherein said compressible membercomprises an inflatable bladder.
 9. The prosthetic foot of claim 1additionally comprising one or more compressible pads disposed on thelower surface of said prosthesis such that they provide cushioning tosaid prosthesis during use by the wearer.
 10. The prosthetic foot ofclaim 1 additionally comprising a resilient, compressible block disposedbetween said lower section of said auxiliary support member, and saidtoe section of said primary support member such that said block will becompressed during toe-off.
 11. A prosthetic foot comprising: a primarysupport member capable of supporting the amputee, and of providingenergy storage and release, said primary support member having asubstantially vertical attachment section, an intermediate curvilinearankle section curving downward and forward from said attachment section,and an arch section extending forward and downward from said anklesection, said upper section being non-rotatably securable to a pylonmember, socket or other prosthetic leg member intermediate said foot andthe stump of an amputee; an auxiliary support member having an uppersection and a lower section, said auxiliary support member being securedwith said arch section of said primary support member at a point on thelower section of said auxiliary support member, said auxiliary supportmember extending rearward and upward substantially along said primarysupport member, said upper section terminating near said attachmentsection of said primary support member; a lower support member having acentral attachment section, a heel section extending substantiallyrearward from said attachment section, and a toe section extendingsubstantially forward from said attachment section, said toe and heelsections providing lever arms for said foot, said attachment section ofsaid lower support member being secured with said auxiliary supportmember and said primary support member at a point along said archsection of said primary support member; whereby said auxiliary supportmember can be easily removed and exchanged without removing said footprosthesis from said prosthetic leg member.
 12. The prosthetic foot ofclaim 9 wherein a restraining element is used to limit the movement ofone member of said prosthesis relative to another member.
 13. Theprosthetic foot of claim 10 wherein said restraining element is a strapof substantially flexible and non-stretchable material.
 14. Theprosthetic foot of claim 10 wherein said restraining element is a strapof substantially flexible and stretchable material.
 15. The prostheticfoot of claim 9 additionally comprising a resilient compressible memberdisposed between said upper section of said auxiliary ankle member andsaid ankle section of said primary support member, said compressiblemember comprising compressible foam.
 16. The prosthetic foot of claim 13wherein said compressible member comprises an inflatable bladder. 17.The prosthetic foot of claim 9 comprising a substantiallynon-compressible friction-reducing element disposed between said uppersection of said auxiliary ankle member and said ankle section of saidprimary support member.
 18. The prosthetic foot of claim 9 additionallycomprising one or more compressible pads disposed on the lower surfaceof said prosthesis, such that they provide cushioning to said prosthesisduring use by the wearer.
 19. The prosthetic foot of claim 9additionally comprising a resilient, compressible block disposed betweensaid lower section of said auxiliary support member, and said toesection of said primary support member such that said block will becompressed during toe-off.
 20. The prosthetic foot of claim 9 whereinsaid arch portion of said forefoot member terminates in anupward-curving tip above said toe portion of said sole member,wherebetween a substantially resilient, compressible control block isdisposed, and additionally comprising a substantially resilient,compressible control block disposed between said lower section of saidauxiliary support member, and said primary support member such that saidblocks would be compressed during toe-off.
 21. A prosthetic foot,comprising: a resilient forefoot member for attachment to an artificialleg; a sole member attached to said forefoot member; and a stiffeningmember removably attached to a point substantially near the lower end ofsaid forefoot member such that it alters the resilience of said forefootmember.